The sensors could be utilized as a part of measuring the radiation temperature without any contact. For different radiation temperature ranges various filters are available. An infrared (IR) sensor is an electronic device that radiates or locates infrared radiation to sense some part of its surroundings. They are undetectable to human eyes.
An infrared sensor could be considered a Polaroid that briefly recalls how an area’s infrared radiation shows up. It is very regular for an infrared sensor to be coordinated into movement indicators like those utilized as a feature of private or business security systems. An IR sensor is shown in figure; basically it has two terminals positive and negative. These sensors are undetectable to human eyes. They can measure the heat of an object and also identify movement. The region wavelength roughly from 0.75µm to 1000 µm is the IR region. The wavelength region of 0.75µm to 3 µm is called close infrared, the region from 3 µm to 6 µm is called mid infrared and the region higher than 6 µm is called far infrared. IR sensors emits at a frequency of 38 KHz.
Features of IR Sensor :
- Input voltage: 5VDC
- Sensing Range: 5cm
- Output signal: analog voltage
- Emitting element: Infrared LED
Example interfacing circuit of IR diode and photodiode
IR sensors mostly used in radiation thermometer, gas analyzers, industrial applications, IR imaging devices, tracking, and human body detection, communication and health hazards.
Here is a brief description of IR & Photo diode sensing switch, let’s see:
An IR diode is connected through a resistance to the dc supply. A photo diode is connected in reverse biased condition through a potential divider of a 10k variable resistance and 1k in series to the base of the transistor. While the IR rays fall on the reverse biased photo diode it conducts that causes a voltage at the base of the transistor. The transistor then works like a switch while the collector goes to ground. Once the IR rays are obstructed the driving voltage is not available to the transistor thus its collector goes high. This low to high logic can be used for the microcontroller input for any action as per the program.
SHRIRAM SPARK 